Not an expert, as I've never tried them, but from what I've seen of the 'mericans posts, they can get a set from one of their local stores for silly cheap money compared to what Triumph are asking.
Hopefully, one of them will be on soon to point you in the right direction.
Thanks Duke - yes, theyre the ones, but we don't have Walmart in the UK. Wonder idf Asda do them, as they were bought by Walmart. Don't think so, but might be worth a look.